The present invention relates to ophthalmic lenses employed in connection with ophthalmic diagnostic and surgical procedures, and more particularly to a compound ophthalmic lens that is utilized for observation of the fundus and for delivery of a laser beam to the fundus.
Ophthalmic lenses are conventionally utilized for observation of various locations within the eye by ophthalmologists. These ophthalmic lenses normally include a contact lens, that is a lens that directly contacts the cornea of the eye, and an entry lens that is spaced in the anterior direction from the contact lens. The objective lens usually magnifies that portion of the eye being observed. The two lenses are normally joined by a housing. Mirrors are sometimes interposed between the contact lens and the entry lens to increase the field that can be viewed by the physician through the lens.
Most ophthalmic lenses of the type just described have been created and designed for use as an observation tool utilized in conjunction with a slit lamp or ophthalmic microscope employed by ophthalmologists. While most prior lenses function reasonably well for use as an observation tool, the advent of laser microsurgery and the accompanying need to deliver a laser beam safely within the eye has created a need for ophthalmic lenses that not only provide improved images of the desired location in the eye, but also have the capability to deliver laser energy to the desired location with minimum effect on other portions of the eye.
One example of the use of laser energy is in connection with the treatment of a patient's fundus. This treatment requires not only the capability to observe the fundus over a wide angle but the capability of being able to deliver a laser beam within the eye and focus it on the fundus. The only lens currently available for wide field fundus observation has at least three elements. The lens forms a real image within the final lens element. While the fundus image so created is adequate, axial magnification is poor, and the internal and external reflections caused by the various lens elements degrades the overall image available and reduces fundus detail if the ocular media is hazy. Moreover, the prior lens exhibits aberrations around the peripheral portion of the image and laser delivery to the peripheral retina is adversely affected by beam astigmatism induced by the lens. Of even more concern is the small beam diameter produced by the prior lens at the level of the cornea and crystalline lens. This small beam diameter has been shown to be potentially hazardous to these structures.